Ceramic vacuum tube



July 10, 1956 H. E. soRG CERAMIC VACUUM TUBE 3 Sheets-Sheet l Filed Aug.l, 1952 l l l r.

INVENTOR. Haro/a E. orj BY ATTORNEY July 10, 1956 H. E. soRG CERAMICVACUUM TUBE 3 Sheets-Sheet 2 Filed Aug. l, 1952 IIIIIIIIII l INVENTOR.Haro/a E. 50/9 BY Ml@ ATTORNEY July 10, 1956 H. E. SRG

CERAMIC VACUUM TUBE 's sheets-sheet s Filed Aug. l, 1952 /1/ Il l lllINVENTOR. Haro/d E. Sorg BY MM? ATTO/QNEY nited States Patent O CERAMICVACUUM TUBE Hamid E. Sorg, Redwood City, Calif., assignor to Eitel-MeCuilough, Inc., ASan Bruno, Calif., a corporation of CaliforniaApplication August 1, 1952, Serial No. 302,175

3 Claims. (Cl. 313-450) My invention relates to electron tubes `and moreparticularly to improvements in the mechanical construction and assemblyof such tubes.

Vacuum tubes in the past -have not been dependable in many types ofelectronic equipments, both commercial and military, because of failuresattributable to the fragile construction of the tubes. `Such lfailuresare largely due to the inherent weakness of mechanical designs employedin the glass tubes which grew out of the old lamp industry. Electrontubes, particularly in the receiving tube category, have served a goodpurpose in home receiving sets and other amusement devices but leavemuch to be desired with regard to dependability and ruggedness underadverse conditions such as shock and vibration and elevated temperatureenvironments.

The broad object of my invention is to overcome the above limitations byproviding a tube -having a ceramic envelope which is of compact andrugged construction.

Another object is to provide improvements in the internal electrodestructure, in combination with the ceramic envelope.

Still another object is to provide a tube `assembly suitable for avariety of tube types, such as diodes, triodes, etc.

A further object is to provide a tube structure which is designed tofacilitate fabrication and which is adaptable for automatic assemblyoperations.

The invention possesses other objects and features of advantage, some ofwhich with the foregoing, will be set forth in the following descriptionof my invention. It is to be understood that I do not limit myself tothis disclosure of species of my invention as I may adopt variantembodiments thereof within the'scope of the claims.

Referring to the drawings:

Figure l is an exploded View of a diode type of tube embodying myinvention.

Figure 2 is a cross-sectional view of the assembled diode; and

Figure 3 is a side elevational view of the same.

Figures 4, 5 and 6 are similar views showing a triode type of tube; and

Figures 7, 8 and 9 are Vcomparable views showing a tetrode.

in greater detail and referring first to Figures l, 2 and 3, my improvedtube structure comprises an all-ceramic envelope which has the generalshape of a at cylinder. Considered as a tube in the receiving tubecategory the views shown are quite enlarged, an actual tube being of theorder of say 3A; inch diameter. The envelope comprises disk-shaped upperand lower end walls 2 and 3 of ceramic and a cylindrical side wall 4also of ceramic. The ceramic used in making vup the envelope ispreferably an alumina type body, as such ceramics have good mechanicalstrength and are able to withstand high temperatures. Other commerciallyavailable ceramics, such as the Zircon type bodies, may 'also =be used.

To facilitate assembly thewallipieces are preferably intertitted at thejoints `for self-.alignment of the parts. ln the constructionillustrated, `the parts are notched or barium-strontium oxides.

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recessed along the edges so as to provide .an interlocking type ofjoint. The ceramic wall pieces are metallically bonded together alongthe upper and Alower joints 6 and 7 to form vacuum-tight seals. Themetal bonding layers at these joints also function as lead-in conductorsfor the electrodes as hereinafter described.

The ceramic-to-ceramic seals may be made in several ways using knownmetalizing and brabing techniques. For example, the opposed surfaces ofthe ceramics at the joints may be coated with nely divided metal powderand tired to sinter the metal particles to the ceramic. A satisfactoryprocedure yis to coat with a mixture of molybdenurn and manganesepowders and fire in hydrogen to a temperature of about C. This producesa thin layer firmly bonded to the ceramic. The sintered area is thenpreferably electroplated with nickel to produce a solid metal surface.Another metalizing technique is to paint titanium or zirconium hydridepowders on the ceramic and lire in vacuum to about 1200 C.

The metalized ceramics may then be brazed or soldered togeher withsilver solder or brazing alloys such as silvercopper, gold-copper or thelike. The brazes are readily made by fitting the ceramic envelopesections together with rings of wire solder adjacent :the joint and thenelevating the temperature of the whole up to the melting point of thesolder in a suitable furnace.v The solder or brazing alloy ows betweenthe metalized ceramic surfaces at the joint and produces a seal which isvacuumtight and strong mechanically. The vjoint also provides a goodelectrical conductor leading into the envelope.

In my tube the upper end wall .Z also functions as the anode, the innerface of the ceramic being metalized as above described to provide theactive anode surface 8. Ceramics such as the alumina type ceramic bodiesare quite good heat conductors and will adequately dissipate the heat insmall tubes having relatively .low anode dissipation ratings. Anodeterminal 9 is also formed by a metalized area on the ceramic envelope,preferably along the peripheral edge of end wall 2 to form a ring-shapedterminal. As shown in Figure l, the anode face 8 and anode terminal 9are connected by the metalized region across the joint, these severalareas lbeing covered by a continuous coating and preferably metalized atthe same time.

The .cathode in my tube is supported by the lower end wall 3 andpreferably comprises a cup-shaped cathode body 11, say of nickel, coatedon the upper surface with an electron emissive material 12 such as theconventional Cathode 11 is preferably engaged over a circular inwardlyprojecting portion of the ceramic Wall for alignment purposes and theflange of the cathode is preferably outturned to provide a lip 13. Thislip is brazed or spotwelded to the metalized inner surface 14 of the endwall, which metalized area extends across the joint region and alsoalong the outer peripheral edge to form the cathode terminal 16. Theheater for cathode 11 preferably comprises a dat spiral of heater wire17 embedded 'in a suitable insulating material 18. One end of the heatercoil is connected to cathode body 11 and the other end is brought out toa separate terminal.

In the tube illustrated a metal exhaust tubulation 19 extends downwardlyfrom the lower wall 3, which 'tubulation is pinched off at tip 21 afterevacuation of the envelope. This tubulation is fitted in a central holehaving a metalized inner surface and is secured by a braze 22 to suchsurface. The tubulation 1'9 also functions as a lead-in conductor for anend of the cathode heater. A metal cap 23 over the tubulation provides abuttonlike terminal.

The metalized areas on the envelope-parts are shown as havingappreciable thickness for convenience of .illustration. Actually theseare quite thin metal layers, say of 3 the order of 0.005" thickness, andappear as films or metal skins on the surfaces of the ceramic. Suchmetalized areas have good electrical conductivity, make excellentterminal surfaces and are ideal for brazing operations.

In the assembly of my tube the ceramic wall sections are first metalizedand then the cathode structure and exhaust tubulation are mounted inplace on the lower wall. The side wall section is then tted between theend walls and the envelope is sealed by brazing at the joints 6 and 7.These joints may be brazed separately or simultaneously. After nalbrazing the tube is ready for exhaust and may be evacuated in the usualmanner. An important feature of this type tube structure and assembly isthat the envelope wall section 4 functions as a spacer element toestablish the cathode-to-anode spacing in the tube. Since the ceramicsare strong mechanically and can be ground to precise dimensions theelectrode spacing is accurated determined.

Figures 4, 5 and 6 show my improved tube structure embodied in a triodehaving a control grid 24. The cathode supporting lower wall 3, anodeforming upper wall 2 and side Wall section 4 are similar to thosedescribed for the diode structure and are like numbered. The added partscomprise the grid structure 24 and a second side wall section 26.Ceramic section 26 is notched or recessed like the lower side wallsection so that it fits anode forming end wall 2. The adjacent notchededges of wall sections 4 and 26 provide an interior groove for holdingthe grid.

Grid 24 is a at disk-shaped type of structure having parallel wiremounted on a supporting ring 27 of metal. This grid ring is engaged inthe above mentioned groove and is brazed between the metalized side wallsections. A metalized strip on the side wall of the envelope providesthe grid terminal 28 which connects with the grid through theintermediate joint 29.

The diode thus forms the foundation structure for the triode, the latterrequiring merely the addition of the grid disk 24-27 and the extra Wallsection 26. As in the case of the diode, the electrode spacings in thetriode are established by the envelope sections, thus, thegridto-cathode spacing is set by the ceramic section 4 and thegrid-to-anode spacing is determined by ceramic section 26. Anotherimportant feature is that the grid is positively and rigidly held by thebrazed connection between the envelope sections.

Figures 7, 8 and 9 shown my improvements embodied in a tetrode having anadded screen grid 30. Here again the tube components follow the triodestructure and are like numbered. The added parts comprise the screengrid structure 30 and a third side wall section 29. Ceramic section 29is notched or recessed like t'ne other wall sections so that it tits theanode forming end wall 2. The adjacent notched edges of wall sections 26and 29 provide a second interior groove for holding the screen grid.

Screen grid 30 is alsoa at disk-shaped type of structure having parallelwires mounted on a metal supporting ring 31. This ring is engaged in thegroove and brazed between metalized ceramic sections 26 and 29. Ametalized strip on the side wall of the envelope provides a screen gridterminal 32 which connects with the grid through the second intermediatejoint 33.

The triode thus forms the foundation structure for the tetrode, thelatter requiring merely the addition of the screen grid disk 30-31 andthe extra wall section 29. As in the case of the diode and triode, theelectrode spacings in the tetrode are established by the envelopesections. This stacking procedure may be continued to produce stillfurther tube types. For example, the addition of another wall sectionand another grid (serving as a suppressor grid) would produce a pentode.

There are many advantages to my improved tube structure, some of whichhave already been mentioned. Another important advantage comes aboutbecause of utter simplicity of the structure and the stackingarrangement which permits a variety of types to be built up from commonparts. The metalized envelope sections and electrodes may be assembledby simple stacking operations, which can be done by automatic machinery.When stacked with rings of suitable brazing material adjacent thejoints, the entire tube may be brazed together in one operation in afurnace. This is all very desirable from an economic manufacturingstandpoint. Probably the greatest advantages, however, have to do withimproved tube reliability. My tube structure is extremely strongmechanically and has Vexcellent thermal resistance properties for hightemperature operation. Tube failures hertoforewue to the fragileconstruction of glass type tubes are largely or completely eliminated.The allcerarnic brazed type of construction is compact and inherentlyrugged and provides a tube which will withstand shock and vibration andwill operate satisfactorily in elevated temperature environments.

I claim:

l. An electron tube comprising a generally cylindrical envelope havingupper/and lower disk-shaped end walls of ceramic, a cylindrical sidewall of ceramic tted to the end walls along upper and lower joints,metallic bonds uniting the ceramic parts together at said joints, theinner face of the upper ceramic wall being metalized, providing ananode, a cathode supported on the lower wall and having an electronemitting surface facing the anode, the metallic bond at the upper jointproviding a lead-in conductor for the anode and the metallic bond at thelower joint providing a lead-in conductor for the cathode, said ceramicside wall comprising a pair of sections fitted together at a joint lyingintermediate the end walls, a metallic bond uniting the side wallsections together at the last mentioned joint, and a disk-shaped gridinterposed between the cathode and anode, said grid having a supportingring engaged between the side wall sections, the metallic bond at theintermediate joint providing a lead-in conductor for the grid. Y

2. An electron tube comprising a generally cylindrical envelope havingupper and lower disk-shaped end walls of ceramic, a cylindrical sidewall of ceramic iitted to the end walls along upper and lower joints,metallic bonds uniting the ceramic parts together at said joints, theinner face of the upper ceramic wall being metalized, providing ananode, a cathode supported on the lower wall and having an electronemitting surface facing the anode, the metallic bond at the upper jointproviding a lead-in conductor for the anode and the metallic bond at thelower joint providing a lead-in conductor for the cathode, said ceramicside wall comprising a pair of sections fitted together at a joint lyingintermediate the end walls, a metallic bond uniting the side wallsections together at the last mentioned joint, and a disk-shaped gridinterposed between the cathode and anode, the side wall having a grooveat the joint between the sections, said grid having a supporting ringengaged in said groove, the metallic bond at the intermediate jointproviding a lead-in conductor for the grid.

3. An electron tube comprising a generally cylindrical envelope havingupper and lower disk-shaped end walls of ceramic, a cylindrical sidewall of ceramic fitted to the end walls along upper and lower joints,metallic bonds uniting the ceramic parts together at said joints, theinner face of the upper ceramic wall being metalized, providing ananode, a cathode supported on the lower wall and having an electronemitting surface facing the anode, the metallic bond at the upper jointproviding a lead-in conductor for the anode and the metallic bond at thelower joint providing a lead-in conductor for the cathode, said ceramicsidewall comprising a plurality of stacked sections iitted together atvertically spaced joints lying intermediate the end Walls, metallicbonds uniting the side Wall 5 sections together at the last mentionedjoints, and diskshaped grids interposed between the cathode and anode,the side Wall having grooves at the joints between the sections, saidgrids having supporting rings engaged in said grooves, the metallicbonds at the intermediate joints providing lead-in conductors for thegrids.

References Cited in the le of this patent UNITED STATES PATENTS PassargeNov. 16, 1937 Binneweg Mar. 7, 1944 Eitel et a1 Feb. 17, 1953 Sorg July28, 1953

1. AN ELECTRON TUBE COMPRISING A GENERALLY CYLINDRICAL ENVELOPE HAVINGUPPER AND LOWER DISK-SHAPED END WALLS OF CERAMIC, A CYLINDRICAL SIDEWALL OF CERAMIC FITTED TO THE END WALLS ALONG UPPER AND LOWER JOINTS,METALLIC BONDS UNITING THE CERAMIC PARTS TOGETHER AT SAID JOINTS, THEINNER FACE OF THE UPPER CERAMIC WALL BEING METALIZED, PROVIDING ANANODE, A CATHODE SUPPORTED ON THE LOWER WALL AND HAVING AN ELECTRONEMITTING SURFACE FACING THE ANODE, THE METALLIC BOND AT THE UPPER JOINTPROVIDING A LEAD-IN CONDUCTOR FOR THE ANODE AND THE METALLIC BOND AT THELOWER